A fork-lift truck usually has a vehicular body constituting a support on which is typically mounted a pair of masts spaced apart transversely relative to the normal direction of travel of the body. Suspended from the masts by means of a flexible element such as a cable or chain is a carriage provided with the load-engaging fork. A hydraulic ram is provided that is extensible against a pulley over which the flexible element is passed so that on extension this ram causes the carriage hung on the flexible element to be raised.
In most such arrangements each mast is formed of a fixed channel portion and a vertically displaceable channel portion slidable by means of hydraulic pressure in the fixed portion. One of these portions is usually operated by a cylinder and the other by a piston. In order to achieve a high lift it is known to provide multiple-stage rams. All such structures, however, are relatively complicated and are both inadequately rigid when extended and excessively complex so that their use in very dirty conditions requires frequent overhaul.